Interlock control system

ABSTRACT

Safety apparatus in the form of an ignition interlock for a powered work unit, particularly one using a magneto ignition engine. An electrical control circuit has a switch which when closed shorts the magneto to ground. An element in the transmission and associated with a gear selector maintains the switch open when the transmission is not in gear and provides for/its closing concomitantly with shifting into any gear. An energizable relay in the electrical circuit provides that once the engine is started and running it will continue to run, in or out of gear, until shut off.

[ 1 Sept. 5, 1972 [54] INTERLOCK CONTROL SYSTEM [72] Inventors: Jerry L. Smith,'3008 Imperial Blvd., Springfield, Ohio 45503; Robert B.

Mead, 1013 North Lincoln, Wilmington, Ohio 45177 [22] Filed: March 5, 1971 21 Appl. 190.; 121,324

521 U.S. Cl ...307/9, 180/4, 123/179 K s 1 1111.131. ..H02g 3/00 [58] Field of Search ..l80/82.4, 82, 103; 191/8; 123/179 K; 307/9, '10

[56] References Cited UNITED STATES PATENTS 3,518,979 7/1970 Harkness 123/179 K 3,028,926 4/1962 Spicer, 'Jr...- ..l80/82.4

11/1966 Baker ..180/82.4 8/1961 Russey et a1. ..123/l79 K Primary Examiner-Herman J. Hohauser Attorney-Jerome P. Bloom [57] ABSTRACT Safety apparatus in the fonn of an ignition interlock for a powered work unit, particularly one using a magneto ignition engine. An electrical control circuit has a switch which when closed shorts the magneto to ground. An element in the transmission and associated with a gear selector maintains the switch open when the transmission is not in gear and provides for/its closing concomitantly with shifting into any gear. An

energizable relay in the electrical circuit provides that once the engine is started and running it will continue to run, in or out of gear, until shut off.

17 Claims, 1 1 Drawing Figures PATENTEDSEP 5 m2 3689.775 sum 1 or 3 "Ill-- JERRY L.SM|TH ROBERT B. MEAD A TTORNE Y nv VEN rans- PATENTEBSEP 5 I972 .3 689.775

. SHEET 3 or 3 IMAGNETOI 80 FIG-IO 105 5 INVENTORS JERRY -L. SMITH ROBERT B. MEAD Arrow/v5) INTERLOCK CONTROL SYSTEM BACKGROUND OF THE INVENTION This invention relatesto improvements in ignition and like interlock control systems and, more particularly, to a most simple mechanical arrangement enabling an optimal incorporation of a switch control for such a system in a powered work unit. It has particular advantage for use in riding mowers and will be so described. However, its application is obviously not so limited and such is not intended.

There is danger of malfunction and damage in starting any power driven unit when the drive thereof is coupled or the transmission thereof is in gear. Consider a riding mower, for example absent the proper safety control. If its engine is started with its transmission in gear, there is usually an abrupt, unexpected, and jolting movement of the vehicle. This has, in many cases, resulted in an injury to a rider, a bystander, and even to adjacent property. Ifthe blades of the mower happen to be engaged when the vehicle is unexpectedly started in gear, the dangers are obviously compounded. This problem has reached serious proportions due to the wide use of riding mowers by inexperienced people. As a result, manufacturers have been faced with the absolute necessity of providing the proper safety controls to avoid such occurrences as a vehicle or any related power driven portion thereof starting while its transmission is in gear.

In efiorts to solve the above noted problem in respect to riding mowers, manufacturers have not only had to consider how to insure a positive and proper control of its drive system in starting but also how to do it cheaply. This last is very important due to highly competitive marketing conditions. A further factor which has caused some concern is the difficulty found in arranging an interlock system in a riding mower so it cannot be inadvertently damaged and put out of commission.

The present invention has overcome the problems above noted, in the area of concern. As a result thereof, there is achieved a most compact, simple and economical switch control for an ignition interlock and like system having particular advantage for use in riding mowers and work units of like nature.

SUMMARY OF THE INVENTION The invention illustrates a simple and sure means for applying an effective ignition or like interlock system in a vehicle, or, for that matter, any power driven work unit. It provides improvements in switch units and controls therefor. As here illustrated in a riding mower, by way of example, it is a characteristic of the invention system that its switch control is distinctively embodied in and moves with an element of the gear shifting mechanism of the vehicle transmission unit.

A primary object of the invention is to provide improvements in ignition interlock and like systems which are economical to fabricate, more efficient and satisfactory in use, adaptable to a wide variety of application and unlikely to malfunction.

Another object of the invention is to provide a more compact switch unit and control therefor in an ignition or like interlock system. i

A further object of the invention is to provide a unique switch control arrangement for an ignition or like interlock system in conjunction with a powered transmission unit.

An additional object of the invention is to provide, in integrated relation to a transmission or like unit, means for effectively inhibiting a direct or indirect drive from said unit unless the same is first started in neutral.

A further object of the invention is to provide an improved safety control interrelated with'the transmission or like segment of a power driven unit possessing the advantageous structural features, the inherent meritorious characteristics and the means and mode of use herein described.

With the above and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof, and the mode of operation as hereinafter described or illustrated in the accompanying drawings, or their equivalents.

Referring to the accompanying drawings, wherein some but not necessarily the only forms of embodiment of the invention are shown,

FIG. 1 is a side elevation of a transmission unit, partially in section, with details shown in a diagrammatic fashion, non-pertinent detail having been eliminated for clarity of disclosure;

FIG. 2 is a view taken on line 2-2 of FIG. 1;

FIG. 3 is a view of a fragment of the structure shown in FIG. 2, with the backing plate removed;

FIG. 4 is a top view of the transmission unit with parts removed for clarity of disclosure;

FIG. 5 is a view taken on line 5-5 of FIG. 4;

FIG. 6 is a view taken on line 6-6 of FIG. 4;

FIG. 7 is a view taken on line 7-7 of FIG. 4;

FIG. 8 is an end elevation view of the controls illustrated in FIG. 4;

FIG. 9 is an illustration of a bracket which mounts the controls shown in FIG. 8;

FIG. 10 is a schematic pertinent to the invention system; and

FIG. 11 is a fragmentary view illustrating a further form of embodiment of the invention.

Like parts are indicated by similar characters of reference throughout the several views.

In the embodiment here described the invention is shown in conjunction with and in application to a multi-speed transmission unit 10 of the type used in riding mowers. As seen in the drawings, the unit 10 includes a shell-like housing formed in two parts, the bottom half 13 of which nests conventional shaft mounted transmission gears. Connected for optional coupling to such gears is an input shaft 11. When the system is coupled, to a degree depending on gear position, power from the shaft 11 is transmitted to and through an output shaft 17. The latter has fixed thereto, externally of the transmission housing, a drive member 15.

Only so must of the unit 10 is here illustrated as may be necessary for an understanding of the invention. The remaining details thereof, particularly as to the gearing, may be such as illustrated in the U.S. Pat. No. Re 26,633 to Orly Musgrave on July 29, 1969.

As shown, the transmission housing is completed and the transmission therein is capped by a shell-like, dome-shaped cover 12 complementary to and mating with the bottom half 13. At its top, the cover 12 includes a flatted outer surface portion 14 having to one end thereof a short vertically projected wall segment 16. The latter has a modified generally rectangular form and a tube-like configuration. In adjacent spaced relation to its upper extremity, the wall segment 16 is bridged by a centrally apertured, transversely disposed, fixed plate segment 18. The segment 18 has its apertured central portion 19 arcuately dished at its upper surface. Releasably fixed over the top of the wall segment 16 is a centrally apertured cap plate 22. The apertures in the plate segment 18 and the cap 22 are so disposed as to be vertically aligned to accomodate the projection therethrough a shift rod 24. Moreover, the central portion 23 of cap 22 is dished in a sense outwardly of the wall segment 16. The arrangement provides for the bearing containment of a ball 26 fixed on the rod 24, to and between the arcuately formed central portions of the plate segment 18 and cap 22. The ball 26 is connected to the rod 24 by suitable means and a pair of trunnions 28 mount therein to project radially therefrom at diametrically opposite positions. As may be seen, the lower or innermost end 30 of rod 24 depends immediately within the shell defined by the cover 12.

A pair of side by side yoke members 32 and 34 are located within the transmission housing immediately below the wall segment 16 and bearing on the inner surface of the cover 12. These yoke members are of identical construction but oppositely disposed. Each includes a generally elongated rectangular plate segment 36 having at one end thereof, bent at right angles thereto and in a sense inwardly of the housing, a relatively short extension 38. Formed integral with the opposite end of each plate segment 36, and similarly bent at right angles thereto, is a yoke finger 40 of plate form.

Each finger is widened as it projects inwardly of the transmission housing and the edge of its projected extremity includes therein an arcuate recess 42 the defining rim of which is formed on a uniform radius. As the plate segments 36 position side by side, they are generally co-planar and their adjacent edges are in substantially bearing contact. This disposes the respective yoke fingers 40 in parallel relation and to respectively opposite ends of the yoke assembly, with their recesses 42 in spaced out coaxial alignment. Attention is directed to the fact that each of the adjacent side edges of the yoke members 32 and 34 includes an identical notch 46 at its center. In the neutral position of the plate segments 36, wherein they are precisely aligned, the notches 46 are thus aligned and open to each other.

A single backing plate 48 is positioned immediately under and held in bearing supporting relation to both the plate segments 36. The plate 48 includes four rectangularly oriented elongate slots 50, commonly directed at right angles to the longitudinal extent of the plate segments 36. The latter have elongate slots 52 in overlying relation and arranged cross-wise to slots 50, at right angles thereto. Projected through the pairs of slots 52 and 50 which are so superposed are control bolts 54. The heads of the bolts 54 abut the surface of the backing plate 48 to the interior of the transmission housing while the upwardly projected ends thereof are suitably engaged in the cover 12. The backing plate 48 also has formed therein a further slot 58 which is centered between the slots 50 and oriented to extend in a sense at right angles to the longitudinal extent of such slots. In the neutral position of the plate segments 36 and the plate 48 the slot 58 is under the notches 46 in the plate segments 36 and in simultaneously bridging relation to the adjacent edges of the plate segments. With this arrangement, the inner end 30 of the shift rod 24, being projected into the slot 58, is also in simultaneous bridging relation to the plate segments 36. Such being the case, the position of the shift rod is such that it is unable to laterally shift either of the plate segments. The shift rod can be moved, to the extent permitted by the backing plate 48, completely into one or the other of the notches 46 and only in this instance can the plate segment 36, in the notch of which the shift rod extremity 30 is disposed, be shifted laterally, one way or the other. Depending upon which direction the rod is shified and in which notch 46 the extremity 30 of the shift rod may be disposed, one can achieve a particular geared arrangement in the transmission unit to provide for a desired output. As will be obvious, the limits of the movements of the backing plate and the respective yoke members are determined by the slots therein, and within the limits controlled by the bolts 54.

Thus, as described, the rod 24 has a neutral position with the end 30 thereof centered as shown in FIGS. 2 and 3 of the drawings in respect to the notches 46, it being understood that in such case'the yoke members 32 and 34 will have to be precisely aligned in side by side relation. This is the neutral control position and, as will be described, the only one in the example illustrated in which a power source, such as an engine, related to the transmission unit can be started.

As can be seen in FIG. 5 and as more particularly evidenced with reference to U.S. Pat. No. Re 26,633 aforementioned, in this neutral position of the parts the spaced parallel yoke fingers 40 depend to respectively engage in a circumferential recess in one of a pair of ring-like dog members 60 to thereby hold them uncoupled from the transmission gearing. The dogs 60 slidably mount on a common shaft 61, as seen in FIG. 5, which also mounts certain gears to either side of each dog. The dogs each include lateral projections (not shown) providing the means whereby on shifting one or the other dog, and depending on the direction of shifting, the same can be coupled in mating recesses in the adjacent faces of adjacent gears. This last achieves a selected clutching of the gears and a particularly desired gear transmission of the power input to the transmission unit. The details of this operation is well known to mechanics versed in the art. It is therefore not further described. It is noted that such is not per se required for an understanding of the present invention.

Looking now to backing plate 48, the same includes an outwardlyprojected offset finger 62 in connection with its side edges at positions respectively adjacent each of the four remote corners of the slots 50. The rectangularly projected fingers 62 provide thereby, at each of the opposite sides of plate 48, a recess within which may be accommodated a nesting of an end portion 38 of one yoke member 32 or 34, as the case may require. Note further in FIG. 2 of the drawings that the backing plate 48 is elongated and has one end 64 extended to project beyond the yoke members 32 and 34, in a sense at right angles to the longitudinal extent of the plate segments 36 and is thereby adapted to underlie, in closely spaced relation thereto, the inner surface of the flat top portion 14 of cover 12 which is beyond the wall segment 16. The projected end 64 includes,

immediately inward of its projected extremity, a small round aperture 66 and a dimple in its undersurface forming an upwardly directed arcuate projection 68. The latter is created by dishing the inner surface of plate 48 and the same is disposed on a line with and in transversely spaced relation to the aperture 66.

Considering more specifically the outer surface of the portion 14 of cover 12, the same mounts a bracket 72. This bracket is blanked from a rectangular plate and so formed to have a large generally trapezoidal shaped corner segment 74 bent perpendicular to the remaining portion thereof which provides an L-shaped base 76. The base 76 seats on bosses 73 which elevates the same to position it in a generally parallel relation to of the vertical plate section 74, is positioned remote from the wall segment 16 and arranged generally parallel to the ends of cover 12. Adjacent thereto, the plate segment 74 mounts a switch unit 80 in an elevated relation on its outer side most adjacent one side of the cover 12. The switch embodied in the unit 80 is completely housed except for. a switch operating plunger 82. As the switch is mounted, the plunger 82 depends through an aperture in the bottom of the switch housing to dispose in slightly offset relation to a further aperture 86 in cover portion 12 therebelow. A flat leaf spring 84 is horizontally extended to position in underlying relation to the bottom of the switch housing. One end of the spring 84 is secured on an upwardly projected boss 75 on cover portion 14 while the body thereof extends to have a portion adjacent its projected extremity positioned immediately under the lower extremity of the plunger 82, essentially in contact therewith. The projected extremity of the spring 84, immediately beyond the plunger 82, overlies the aperture 86 which is defined by a tubular boss formed on the cover portion 14 immediately adjacent the wall segment 16. As will be seen from FIG. 1 of the drawings, with the yoke members 32 and 34 and the backing plate 48 in a neutral position, the projection 68 directed upwardly of the extension of the backing plate engages and drives upwardly a pin 88 hearing in the tubular boss defining the aperature 86. In such case the pin 88 is pushed upwardly against the projected extremity of the leaf spring 84 which in turn causes the inward bias of the switch operating plunger 82.

As will be seen, by this means one can control the switch to signal that components of the transmission unit are in neutral position and it is at this point safe to energize the related engine or other power source.

To have a certain definition of this neutral position of the backing plate 48 and a precise frame of reference for control of the switch unit as described, attention is directed to further position defining elements shown in FIGS. 4 and 7 of the drawings. It may be here seen that in laterally spaced relation to the aperture 86 in the cover portion 14 is a further aperture defined by the open end of a tubular housing 90. The latter contains a ball member 92 backed by a coil spring 94 which tends to bias the ball member 92 in a sense inwardly of the transmission housing. In the shifting of the backing plate in the course of shifting the gears of the transmission unit disclosed, the ball 92 will bear on the upper surface of the extension 64 of the backing plate 48 and in the precise neutral position thereof the ball 92 will seat in the upper portion of the aperture 66. Of course, at this time, simultaneously the projection 68 functions to operate the plunger 82 of the switch unit- 80. Thus, the extension of thebacking plate has a switch operating member functioning in the neutral position thereof and the precise location for function is precisely defined by the engagement simultaneously of the ball 92 in the aperture 66. This insures that there is no fluttering in making the plunger contact and there is a clear definition of a condition in which. the controls will enable a starting of the related engine.

Looking further to the basic elements of the control circuit provided in the embodiment illustrated, there is mounted on the base of the bracket 72, along the edge remote from the switch unit 80, a spring clip forming a saddle 96 which receives therein a capacitor 98. Also fixed to the base of the bracket 72, between the capacitor 98 and the switch unit 80, is a normally closed relay 102. In side by side relation to the relay is a diode 104.

Now referring to FIG. 10, it may be seen that the capacitor 98 is connected across the relay 102 and the diode 104 is connected between one side of the switch and the relay, a lead element 105 being extended to connect to the magneto of the related engine.

FIG. 10 illustrates the condition of the control circuit in question when the transmission is not in neutral. If the engine has stopped with the transmission in gear, then thecontacts of switch unit 80 are closed as shown. This will produce a ground in connection with the engine ignition circuit, as conventionally provided, and prevents starting the engine until the switch contacts are open. According to the present invention, where the transmission is in gear, the backing plate 48 and its extension 64 will be in a position accommodating the projection of pin 88 inwardly of the transmission housing. Thus, there will be no bias of the leaf spring 84 and the plunger 82 will be fully dependent from the switch housing. Also, under such circumstances the projection 68 of the backing plate 48 is displaced from pin 88 and the ball 92 is biased into its housing under the influence of the backing plate extension 64. When, and only when, the shift rod 24 is in a neutral position, where the input to the transmission housing is disengaged from the transmission gears, then projection 68 and aperture 66 respectively come under pin 88 and ball 92, the latter entering aperture 66 to releasably fix the position of the plate 48. The projection 68 in this position will be positively centered to exert leverage through the spring 84, by way of pin 88, to lift plunger 82 and thereby cause a opening of the contacts in the switch unit 80, the elements thereof being appropriately so provided. With these switch contacts opened, the ignition control circuit is cured of its ground and the engine may then be started. As will be obvious, the engine cannot be started before the controls are in their precisely required position.

From the foregoing it will be seen that the invention is extremely simplein concept yet it affords a direct and precise means which may be integrated in the transmission unit per se or in conjunction therewith in a highly economical manner. Moreover, the manner of incorporation lends insured function as and when required.

The precise arrangement of the switch controls as here-provided is enhanced by the simple mount of the basic essentials of the ignition control circuit. The single bracket mount provides a relation of the components in exceedingly compact form facilitating the occupancy of a minimal amount of space in application to the transmission housing. The arrangement is such to avoid the inadvertent interference with or damage to the control system.

Attention is now directed to FIG. 11 of the drawing wherein a slightly different arrangement may be provided for the mount of the switch unit. In this case, the switch unit 80 may be mounted to a bracket 106 on an extension 108 of the wall segment 16. In the extension 108 is formed a tubular housing containing a coil spring 110 which surrounds the plunger 82' constituting the operating element of the switch unit 80'. At the lower end of the plunger is an expanded head 112 which projects through an opening at the bottom of the plunger housing, exposed thereby to the extension 64 of the backing plate 48. Of course, in this case the apex of the head 112 would be in a position to project through the transmission cover 12 at the same point that the pin 88 projects therethrough in the embodiment first described. Thus with the parts of the transmission unit in neutral position the projection 68 on the backing plate 48 shown in neutral position in FIG. 11 will move to a position biasing upward the plunger 82 through the medium of its head 112. This will open the contacts in the switch unit 80 and serve the function previously described.

In the modification shown in FIG. 11, there still will be the provision for the housing and function of the ball 92 in respect to the cover 12 and the backing plate 48 as previously described. The ball 92 in any case will establish precisely the position of the backing plate in its neutral orientation, the ball 92 seating in the upper portion of the aperture 66 as previously described. Of course, the remaining components of the ignition control circuit can be disposed in relation to the bracket 106 in a manner similarly as described with reference to the bracket 72.

The last described embodiment of the invention shown in FIG. 11 is not preferred. However, it shows another form of embodiment of the invention that may be desirable where the orientation of the transmission unit and the arrangement of its superstructure may so dictate. The difference here is that the basic elements of the controls are consolidated more vertically.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing of its advantages.

While in order to comply with the statute the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise but one of several modes of putting the invention into effect and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described my invention, I claim:

1. In a powered work unit, having an energizable power source including drive means and a power transmission device including means for coupling and uncoupling said drive means in respect to elements to be driven thereby, safety apparatus in the form of an ignition interlock system including means defining a control circuit connected to normally inhibit the energizing of said power source unless its drive means is uncoupled, said control circuit including switch means, said switch means mounting to said transmission device and having in direct operative relation thereto an element of said transmission device the position of which conditions said switch means in correspondence with the coupled or uncoupled condition of said transmission device to provide a condition of said control circuit enabling the energizing of said power source only in the uncoupled condition of said transmission device.

2. Apparatus as set forth in claim 1 characterized by said transmission device including a shifting element the position of which dictates the coupled or uncoupled condition of said transmission device and said element in operative relation to said switch means being operatively related to said shifting element for movement thereby.

3. Apparatus as set forth in claim 1 characterized by said transmission device including a housing, said housing containing a plurality of drive elements and means for coupling said drive means to selective of said drive elements or disengaging said drive means from said drive elements, said last named means including said element in operative relation to said switch means in operative connection therewith, the last said element being positioned by and in accordance with the position of said last named means.

4. Apparatus as set forth in claim 3 wherein said switch means is mounted to said housing and has directed therefrom a control element and said element in direct operative relation to said switch means having a portion to selectively operates said projected control element to condition said control circuit to enable the energizing of said power source.

5. Apparatus as set forth in claim 4 wherein said element in direct operative relation to said projected element of said switch means is a plate element and said plate element has in operative relation thereto means for frictionally holding the same in a position to provide a precise reference thereof to the projected element of said switch unit and thereby insure the enabling of the energizing of said power source as and when required.

6. Apparatus as set forth in claim 1 wherein said power transmission device includes a housing and said switch means mounted directly on said housing, said switch means having a projected control element arranged in operatively exposed relation to control means in the interior of said housing, the said control means being in the path of said element in direct operative relation to said switch means for control thereby.

7. Apparatus as set forth in claim 1 characterized by a housing for said power transmission device, said housing having projected therein a shift rod for controlling said means for coupling and uncoupling said drive means, said switch means mounting to said housing in adjacent relation to said shift rod and having an exposed control element to which is operatively related said element in direct operative relation thereto.

8. Apparatus as set forth in claim '7 characterized by said element in direct operative relation to said switch means including a plate element connected for movement with said shift rod and means arranged to project therefrom for influencing the operation of said switch means.

9. Apparatus as set forth in claim 1 characterized by a housing for said transmission device, a control member projected in said housing and movable to selectively couple or uncoupled said power transmission device in reference to said power source, said control member having in direct connection therewith a plate member, and means bearing on said plate member in operative connection to said switch means in the uncoupled condition of said transmission device to condition said switch means to enable the energizin of said power source.

10. The apparatus as set forth in claim 9 characterized by a platform on said housing in adjacent relation to said control element, said platform mounting said switch means, said switch means having exposed control means, said housing having therein, in bearing relation thereto, a control pin and said means on said plate member operating on said control pin to cause the same to engage the exposed control means of said switch means to operate said switch means and enable a conditioning of said control circuit to provide for energizing said power source.

11. Apparatus as set forth in claim 10 including a with a capacitor, a relay and a diode which are connected to provide said means defining said control circuit.

13. Apparatus as set forth in claim 12 characterized by a control member mounted to project in said housing for selective movement to direct the coupling or uncoupling of said drive means, said control member being operatively connected to said element, said switch means being fixed closely adjacent said element, mounted to said bracket means to position with a control portion thereof exposed for operation through the medium of said element on movement of saidcontrol member to an uncoupling position while said power source is de-energized whereby to condition said circuit to enable energizing of said power source.

14. Apparatus as set forth in claim 13 wherein said bracket means is a plate including a portion disposing vertically of said housing and mounting said switch in closely embodied relation to said housing.

biasing means connected to said housing a portion of 15. Apparatus as set forth in claim 14 characterized by said plate including a base providing a horizontal platform for elements of said control circuit in compact proximity to said housing.

16. In a powered work unit having a magneto ignition engine and a transmission to couple and uncouple the engine in respect of a driven means, said transmission including a gear selector means; safety apparatus in the form of an ignition interlock providing an electrical control circuit including a magneto, a switch in said circuit which when closed shorts said magneto to ground, and an element in the transmission and operated by a gear selector means therein to maintain said switch open when the transmission is not in gear and to allow it to close concomitantly with shifting into any gear.

17. Safety apparatus according to claim 16, characterized by a relay in said electrical control circuit energized in response to running of the engine precluding shorting of the magneto to provide that once the engine is started and running it will continue to run, in or out of gear, until shut off.

UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION I Patent: No. 3,689 ,775 Dated September 5 1972 Invent0r g Jerry L. Smith Robert B. Mead It is certified that error appears in the above-identified patent and that said Letters Patent arehereby corrected es shown below:

Col 1 11319 'comma i nserted' -followi mz "exaniple".

Col line 10 -f of is inserted following "tfierethrough". Col 3 1 line 44, "out" is corrected. to read but Col 5 line 46, "aperature" should read aperture C01. 8 Claim 4; "line 5, "o'perates" is correcm'd'to read operate Col 8 Claim 6 line 3 "mounted" is corrected to read mounts Col 9 Claim 9 line 4, "uncoupled" is corrected toread un'couple The assignee of record in the above identified patent is Boise Cascade.

' Signed and sealed this 8th day of May l973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents F ORM PO-105O 0-69) USCOMM-DC 6O376-P6D 0.5. GOVERNMINT FR NTING OFFICE ID! 036-63l UNITED STATES PATENT OFFICE I I CERTIFICATE OF CORRECTION Patent No. 7 3,689,775 Dated September 5 1972 Inventor(s) Jerry L. Smith Robert B. Mead v It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col 1 line 15 comma is inserted -following "example".

Col '3 line 10 of is inserted following "therethrough".

Col 3 line 44, "out" is corrected to read but I Col. 5 line 46, "aperature" should read aperture C01 8 Claim 4; line 5 "operates" is corrected to read operate C01 8 Claim 6 line 3 "mounted." is corrected to read I mounts Col. 9 Claim 9 line 4 "uncou'oled" is corrected toread uncouple The assignee of record in the above identified patent is Boise Cascade.

Signed and sealed this 8th day of May 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOITSCHALK Attesting Officer Commissioner of Patents FORM P0-1050 0-69) USCOMM-DC 60376-1 09 Q as oovnmuur rnnmnu omce I!" o-ul-on 

1. In a powered work unit, having an energizable power source including drive means and a power transmission device including means for coupling and uncoupling said drive means in respect to elements to be driven thereby, safety apparatus in the form of an ignition interlock system including means defining a control circuit connected to normally inhibit the energizing of said power source unless its drive means is uncoupled, said control circuit including switch means, said switch means mounting to said transmission device and having in direct operative relation thereto an element of said transmission device the position of which conditions said switch means in correspondence with the coupled or uncoupled condition of said transmission device to provide a condition of said control circuit enabling the energizing of said power source only in the uncoupled condition of said transmission device.
 2. Apparatus as set forth in claim 1 characterized by said transmission device including a shifting element the position of which dictates the coupled or uncoupled condition of said transmission device and said element in operative relation to said switch means being operatively related to said shifting element for movement thereby.
 3. Apparatus as set forth in claim 1 characterized by said transmission device including a housing, said housing containing a plurality of drive elements and means for coupling said drive means to selective of said drive elements or disengaging said drive means from said drive elements, said last named means including said element in operative relation to said switch means in operative connection therewith, the last said element being positioned by and in accordance with the position of said last named means.
 4. Apparatus as set forth in claim 3 wherein said switch means is mounted to said housing and has directed therefrom a control element and said element in direct operative relation to said switch means having a portion to selectively operates said projected control element to condition said control circuit to enable the energizing of said power source.
 5. Apparatus as set forth in claim 4 wherein said element in direct operative relation to said projected element of said switch means is a plate element and said plate element has in operative relation thereto means for frictionally holding the same in a position to provide a precise reference thereof to the projected element of said switch unit and thereby insure the enabling of the energizing of said power source as and when required.
 6. Apparatus as set forth in claim 1 wherein said power transmission device includes a housing and said switch means mounted directLy on said housing, said switch means having a projected control element arranged in operatively exposed relation to control means in the interior of said housing, the said control means being in the path of said element in direct operative relation to said switch means for control thereby.
 7. Apparatus as set forth in claim 1 characterized by a housing for said power transmission device, said housing having projected therein a shift rod for controlling said means for coupling and uncoupling said drive means, said switch means mounting to said housing in adjacent relation to said shift rod and having an exposed control element to which is operatively related said element in direct operative relation thereto.
 8. Apparatus as set forth in claim 7 characterized by said element in direct operative relation to said switch means including a plate element connected for movement with said shift rod and means arranged to project therefrom for influencing the operation of said switch means.
 9. Apparatus as set forth in claim 1 characterized by a housing for said transmission device, a control member projected in said housing and movable to selectively couple or uncoupled said power transmission device in reference to said power source, said control member having in direct connection therewith a plate member, and means bearing on said plate member in operative connection to said switch means in the uncoupled condition of said transmission device to condition said switch means to enable the energizing of said power source.
 10. The apparatus as set forth in claim 9 characterized by a platform on said housing in adjacent relation to said control element, said platform mounting said switch means, said switch means having exposed control means, said housing having therein, in bearing relation thereto, a control pin and said means on said plate member operating on said control pin to cause the same to engage the exposed control means of said switch means to operate said switch means and enable a conditioning of said control circuit to provide for energizing said power source.
 11. Apparatus as set forth in claim 10 including a biasing means connected to said housing a portion of which is interposed between said pin and the exposed control means of said switch means, said pin operating on said control means of said switch means through the medium of said portion of said biasing means and said biasing means being arranged to position said pin means inwardly of said housing when said transmission device is in the uncoupled condition.
 12. Apparatus as set forth in claim 1 characterized by a housing for said transmission device, bracket means on said housing, said bracket means mounting in closely adjacent relation thereon said switch means together with a capacitor, a relay and a diode which are connected to provide said means defining said control circuit.
 13. Apparatus as set forth in claim 12 characterized by a control member mounted to project in said housing for selective movement to direct the coupling or uncoupling of said drive means, said control member being operatively connected to said element, said switch means being fixed closely adjacent said element, mounted to said bracket means to position with a control portion thereof exposed for operation through the medium of said element on movement of said control member to an uncoupling position while said power source is de-energized whereby to condition said circuit to enable energizing of said power source.
 14. Apparatus as set forth in claim 13 wherein said bracket means is a plate including a portion disposing vertically of said housing and mounting said switch in closely embodied relation to said housing.
 15. Apparatus as set forth in claim 14 characterized by said plate including a base providing a horizontal platform for elements of said control circuit in compact proximity to said housing.
 16. In a powered work unit having a magneto ignition engine and a transmission to couple and uncouple the engine in respect of a driven means, said transmission including a gear selector means; safety apparatus in the form of an ignition interlock providing an electrical control circuit including a magneto, a switch in said circuit which when closed shorts said magneto to ground, and an element in the transmission and operated by a gear selector means therein to maintain said switch open when the transmission is not in gear and to allow it to close concomitantly with shifting into any gear.
 17. Safety apparatus according to claim 16, characterized by a relay in said electrical control circuit energized in response to running of the engine precluding shorting of the magneto to provide that once the engine is started and running it will continue to run, in or out of gear, until shut off. 